Effects of extrusion cooking processing on physicochemical properties of aquafeed sinking pellets

In order to large-scale produce a low-pollution, high conversion rate of eco-friendly aquafeed sinking pellets, the formula aquafeed was produced by extrusion cooking processing using a corotating twin-screw extruder, physicochemical properties (expansion ratio, sink rate, bulk density, starch gelatinization and pellet water stability index) of sinking aquafeed using as important index. Response surface methodology (RSM) was used to investigate the effects of feed moisture content (22%-38%), barrel temperature (70-170℃) and screw speed (73-107?r/min) on physicochemical properties of sinking aquafeeds. And microstructure of aquafeeds was analyzed by means of scanning electron microscope (SEM). The results showed that feed moisture content, barrel temperature and screw speed all affected physicochemical properties of extruded aquafeed significantly. Desirable products, characterized by low expansion ratio (1.14), while high bulk density (757.6?g/L), starch gelatinization (879.5?g/kg), pellet durability (96.6%) and water stability index (88.7%), were obtained at medium to high feed moisture content, barrel temperature and low screw speed. SEM examination showed that the microstructure of pellets was smooth and firm, when in the optimal conditions (feed moisture content 31%, barrel temperature 126℃ and screw speed 78 r/min). The results can provide a reference for producing develop efficient, low consumption, high-quality, low-carbon sinking aquatic feed.